BAS Lodgement Guide Australia 2026
"The ATO doesn't care that you forgot what quarter it is."
Business Activity Statement. Four letters. Twelve deadlines per year if you're quarterly. Every quarter, thousands of Australian businesses miss their lodgement deadline — not out of negligence, but because the calculation took longer than expected, the reminder came too late, or the numbers weren't in the right place.
The 2026 BAS Due Dates
For quarterly lodgers, your BAS due dates in 2026 are:
- Q1 (Jul–Sep 2025): Due 28 October 2025
- Q2 (Oct–Dec 2025): Due 28 February 2026
- Q3 (Jan–Mar 2026): Due 28 April 2026
- Q4 (Apr–Jun 2026): Due 28 July 2026
- Monthly lodgers: Due 21st of the following month
Missing these dates triggers Failure to Lodge penalties at $313 per 28-day period. Interest compounds. The ATO does not negotiate deadlines — they're legislated.
What Goes Into Your BAS
Your BAS captures GST collected and GST paid during the period. It also covers PAYG withholding (tax you've withheld from employees), PAYG instalments (prepayment of your own income tax), and fuel tax credits where applicable.
- G1 — Total sales (including GST)
- G2 — Export sales (GST-free)
- G3 — Other GST-free sales
- G10 — Capital purchases over $82.50
- G11 — Non-capital purchases over $82.50
- 1A — GST on sales (G1 ÷ 11)
- 1B — GST on purchases (GST-eligible portion of G11 ÷ 11)
- W1 — Total salary and wages
- W2 — PAYG withheld from payments
The Manual Way vs. The AI Way
The manual BAS process: export transactions from your accounting software, categorise any uncategorised items, run the GST report, reconcile it against your bank, check tax codes, calculate GST payable, complete the form, lodge via the portal. Time: 3–6 hours per quarter for most SMBs.
The XIntelliSync way: the BAS Preparation Agent runs continuously, categorises transactions as they come in, calculates GST in real time, and has your BAS statement ready for review before the deadline arrives. Time: under 10 minutes to review and approve.
Common BAS Mistakes That Cost Australian SMBs
The ATO's compliance data shows these errors appear most frequently:
- Claiming GST on purchases that are GST-free or input-taxed
- Failing to report fringe benefits on BAS
- Incorrect tax codes applied to bank transactions
- Forgetting to include wages in PAYG withholding section
- Missing capital acquisitions on G10
- Lodging the wrong quarter (swapping Q1 and Q3 is common)
The ATO doesn't care that you forgot what quarter it is. The penalty is the same either way. The agents that prepare your BAS automatically do care — which is why they run 12 months before you remember to ask.